Q&A - PSLE Math

[TT2]

:thankyou:

MathIzzzFun:

TT2:

Hi MathIzzzfun,


Thanks for your help. Noticed that e cross-multiply way is sometimes used to solve e ratio problems n sometimes e model method can be used. My son is not familiar on e 1st method. When do we use e cross multiply method or die die must use this? Eg. There is movement of e items???? :? Pls help...... :imdrowning:

Thanks a lot

Hi

I will post the model solution later.. in a rush now.. and also the cross multiply method.

cheers.

[MathIzzzFun]

TT2:

:thankyou:

MathIzzzFun:

[quote=\"TT2\"]Hi MathIzzzfun,


Thanks for your help. Noticed that e cross-multiply way is sometimes used to solve e ratio problems n sometimes e model method can be used. My son is not familiar on e 1st method. When do we use e cross multiply method or die die must use this? Eg. There is movement of e items???? :? Pls help...... :imdrowning:

Thanks a lot

Hi

I will post the model solution later.. in a rush now.. and also the cross multiply method.

cheers.

[/quote]u r welcome

cheers.

[MathIzzzFun]

stary:

Thanks MathIzzzFun for your prompt reply!

u r welcome

cheers.

[stary]

MathIzzzFun:

stary:

Thanks MathIzzzFun for your prompt reply!

u r welcome

cheers.

[Verysuperkiasu]

Have a question on math - if the questions do not require the child to reduce answer to lowest form (for fractions), MUST they do it? Will marks be deducted if they don't? My son's teacher advises them not to reduce to lowest if not specified in the question for fear that the chn may make careless mistakes in the process of reducing to lowest term. However, I seem to recall my time in school, the teacher emphasised MUST reduce fractions to lowest form even if not asked to do so. Has the requirements change since then?

[ozora]

Hi need some help in these 2 questions.


Mac bought some apples and gave half to Jack.
Jack bought some oranges and gave half to Mac.
Mac threw away 25 rotten oranges and Jack bought another 25 apples for himself.
In the end, the number of oranges to the number of apples Mac had was 1:4 and the number of oranges to the number of apples Jack had was 1: 2.
How many oranges did Jack buy?

2.Mr Lee had some buttons for sale. 3/5 of them were black and the rest were white. After selling 120 white buttons and 5/9 of the black buttons, he had 2/5 of the buttons left. How many buttons did he sell in all?

[iFirefly]

Verysuperkiasu:

Have a question on math - if the questions do not require the child to reduce answer to lowest form (for fractions), MUST they do it? Will marks be deducted if they don't? My son's teacher advises them not to reduce to lowest if not specified in the question for fear that the chn may make careless mistakes in the process of reducing to lowest term. However, I seem to recall my time in school, the teacher emphasised MUST reduce fractions to lowest form even if not asked to do so. Has the requirements change since then?

DS says teacher told them must reduce fractions to lowest form, even if question does not specify. DS is from GEP but his friends from mainstream are taught that way too.

[tianzhu]

Hi ozora


Good Morning.

Q1 is a tweaked version of a question from PSLE Maths 2009.
You may solve it using MD or UM.

http://farm7.static.flickr.com/6188/6119123632_b0a9875903_z.jpg\">


For more practice, you may also change the question, instead of Jack buying another 25 apples, change it to Jack buying another 25 oranges.

Mac bought some apples and gave half to Jack.
Jack bought some oranges and gave half to Mac.
Mac threw away 25 rotten oranges and Jack bought another 25 oranges for himself.
In the end, the number of oranges to the number of apples Mac had was 1:4 and the number of oranges to the number of apples Jack had was 1: 2.
How many oranges did Jack buy?


As for Q2, you may use MD or UM to do it.
Not much time, so will share some pointers.

Divide a bar into 15 units.

Black buttons ----- 9units
Black buttons sold ----- 5 units.
Black buttons left ------ 4units

White buttons ------ 6units
White buttons sold ----- 120
White buttons left ------ 6units -120

He had 2/5 of the buttons left.
2/5*15 ------ 6units

6units ------- 4units + (6units - 120)
4units ------ 120
1unit ------ 30

He sold 150 black buttons (5*30) and 120 white buttons

Hence, altogether 270 buttons

Hope this helps.

Best wishes

[Daddy]

Hi GreenBelt,


Thanks, why you used \"5 x 19 = 95cm\". I do not understand. Thanks.

[Daddy]

Hi all,


I have 2 ratio questions that I do not understand how to solve them. Any way or method to understand or solve most of the ration questions. Thanks

Here are the questions. Maybe they are easy question.

1. The ratio of the number of boys to the number of girls was 4:9.
When 17 girls left, the ratio of the number of boys to the number of girls became 6:5. How many children were there at first?

2. English exam, 5/7 of Nicholas' marks was twice of Jonathan's marks.
What is the ratio of Niholas' marks to Jonathan's marks?

Thanks
Daddy